Cowl area Tar and rubber sound deadener material

[Mikesmalaga72]

Has anyone found a source for the correct thickness or very similar greyish rubber vertical sound deadening pads and the 33degree angle tar/bitumen sound deadener unsure if is the same for floor pan sound deadener? Thanks! 

[Conserv]

Mike,

 

I don’t have a replacement for the tar/bitumen sound deadening — I kept my original in place — but I found that neoprene sheets are a very close replacement for the vertical sound deadening in the front of the plenum.

 

It’s available in lots of thicknesses. I don’t recall the specific thickness I chose; it might be 1/8” (?). Just measure the original pads you’re replacing. I used a self-adhesive style of neoprene, and it’s held up very well for 4 years. I always assumed I’d go to a contact cement if the self-adhesive failed. It’s not failed, at least not yet.

 

Regards,

 

Steve

 

[SydneyTii]

I did the same Steve, I used neoprene after removing the bitumen, that was fun…. Not! The sheet on the incline side of the plenum where the heater mounts hides all kinds of nasties from blocked plenum drains, the factory didn’t paint under them before fixing them, I found only primef under mine and lots of surface rust under the bottom edge, which required sanding, priming and painting, I then used clear wax to seal the bottom of the plenum, it’s somewhat of a rust trap spot especially for outdoor cars.

[Conserv]

On 12/23/2021 at 6:50 AM, SydneyTii said:

… the factory didn’t paint under them before fixing them, I found only primer under mine…

 

+1

 

Yep. And, consequently, the car’s exterior paint is on top of the bituminous sheets, but unevenly, more a heavy overspray than finished paint, and with cracks or crevasses in the bituminous sheets still evident. On my ‘76, there was no evidence of rust, so I told my painter to mask off the bituminous sheets and leave them un-touched. He was, yet again, horrified at the factory finish, ignored my directive, and painted them completely and perfectly in Polaris, to improve on the factory finish. This, of course, annoyed me, because I “embrace” the sad factory finishes (?). So… he then masked around the bituminous sheets, leaving only the sheets exposed, roughed up the fresh Polaris paint, painted the pads flat black — to give them that lovely “bituminous” appearance — and then coated the pads with a good Polaris overspray, leaving the pads fairly original looking, but actually encased in layers of un-needed paint! ?

Ahhh: the things we do for love… ?

 

Best regards,

 

Steve

 

[calw]

now that's attention to detail!  But now that you've announced this non-original detail the concourse inspector will be obliged to pry up a corner of the pads!

[Conserv]

5 hours ago, calw said:

now that's attention to detail!  But now that you've announced this non-original detail the concourse inspector will be obliged to pry up a corner of the pads!

And THAT is why you’ll never find my cars in concours events… I’d hate to have to murder some poor inspector! ?

 

Best regards,

 

Steve

 

 

[mac]

Must be another different between roundies and squares.  My '71, '72 & '73 all had the plenum incline panel painted body color.  

The vertical rubber panel was grey.

 

Mac 

[Mikesmalaga72]

Thanks guys you rock!!!! Neoprene it will be! Factory thickness apx .130" Thanks!! 

[John_in_VA]

Please let us know where & what you source as a replacement.

[Mikesmalaga72]

Will do, I might want to laser cut the openings etc.... and make a batch.

 

 

Edited December 24, 2021 by Mikesmalaga72

[PapaG]

Count me in if you do that!

 

[MurphinDC]

Curious question.....I don't have either of these sound deadening pieces in my cowl area and I'm wondering how much they help with deadening the sound?  Is worthwhile to buy some neoprene and install it?  I know these cars are loud, especially above 60mph.

 

@Mikesmalaga72 I'd be in for some if you come up with a solution.

[Mikesmalaga72]

I suppose they are warranted if the BMW engineers designed that in. Unsure of the actual NVH reduction but should be there for at least appearance. 

[Conserv]

On 12/23/2021 at 9:57 PM, Mikesmalaga72 said:

Thanks guys you rock!!!! Neoprene it will be! Factory thickness apx .130" Thanks!! 

Just to be clear, the neoprene was a great replacement for the vertical sound deadening at the front of the plenum in my ‘76. I don’t know if it’s a suitable replacement for the uneven, more horizontal, bituminous sound deadening at the rear of the plenum.

 

Regards,

 

Steve